The present invention relates generally to improvements in electrical distribution raceways and more particularly pertains to new and improved duct apparatus for distributing isolated power and equipotential ground on the surface of walls and ceilings of environments being reworked for isolated power and equipotential ground systems. Isolated power and equipotential ground systems are required, for example, in hospital environments utilizing inhalation anesthetics.
The problems inherent in utilizing electric power in environments containing explosive or flammable gasses is self evident. The problem is most acute in hospital environments wherein both flammable and non-flammable inhalation anesthetics are utilized along with electrically powered equipment. In order to prevent any possibility of a static spark discharge, most operating rooms utilize a controlled 50% humidity and a conductive floor. All personnel working in the area wear conductive shoes. These measures are taken to keep the personnel and equipment in the operating room relatively electrically neutral and prevent a static build up that could result in a point discharge.
Aside from the danger of explosion when flammable anesthetics are utilized, the danger to the patient has served as considerable impetus to prevent stray currents. For example, it only takes on the average of 0.1 to 0.3 amp at 60 cycles applied for one second to cause ventricular fibrillation of the heart when applied externally to the body. It only takes on the average of 10-100 microamps of current at 60 cycles applied for one second to cause ventricular fibrillation of the heart when applied directly to the heart. The heart is exposed during open-heart surgery, for example. Such very small currents must be guarded against for the sake of the patient and the personnel serving him.
As a result of concern for the patient and these inherent dangers in the use of flammable anesthetics, power to a hospital operating room must be supplied through an isolation transformer that has ground-leakage monitoring devices mounted in its secondary. These ground-leakage monitors monitor for any abnormal leakage current flow between either of the secondary power wires and ground. If leakage current flow of a certain amount is detected, then an alarm will be activated. In essence, the ground-leakage monitor indicates equipment failure of the type in which one of the two current-carrying wires is somehow connected, or partially connected, to the frame of the electrical equipment. The National Fire Protection Association Code No. 56A, 1973, requires that all equipment and the patient in a hospital operating room be grounded to an equipotential ground system
An equipotential ground system is required for the reason that small current flows in the ground wires could injure the patient, especially if he is catheterized. If all grounds in an operating room are connected together, any potential difference between the different ground wires is equalized, thereby reducing the danger of injury to the patient as a result of small current flows in the ground system.
Power and ground outlets throughout an operating environment which supply isolated power and equipotential ground points is required by the National Fire Protection Association Code No. 56A, 1973. Hitherto, it has been distributed only in the newer hospitals wherein the isolated power and equipotential ground lines were placed within the confines of the walls of the operating room. Older hospitals, prior to the present invention, were faced with the extremely high expense of distributing the isolated power and equipotential ground only in the interior of the walls of the operating room. This, in essence, meant that such walls had to be torn down and built again.
This is no longer the case. As a result of the present invention, all requirements of the National Fire Protection Association for the distribution of isolated power and equipotential ground is complied with while distributing the same on the surface of existing walls and ceilings.